I also noticed that, though I'd want to know some more details, mostly what "a factor in" means. If it's a stricter definition, where the hitchhiker or the person picking them up committed a crime with the other party as the victim, that does seem like a quite high percentage. On the other hand, I suspect they might be using a very loose definition of "a factor in", where they're counting any crime committed by a person who hitchhiked at any point close in time to the crime, as having been indirectly facilitated by hitchhiking.